Fire retardants are well-known and are typically added to and/or applied as a surface treatment to help prevent the spread of fire and/or protect a material exposed to fire. Commercially available fire retardants may be obtained in great variety, including examples such as bromine-based fire retardants, phosphorous-based fire retardants (e.g., ammonium polyphosphate (APP)), nitrogen-based fire retardants (e.g., melamine), inorganic-based fire retardants, and chlorine-based fire retardants.
A fire retardant can also be classified by the mechanism in which it acts as a fire retardant. For example, a class of fire retardants acts by absorbing heat, thereby cooling the surrounding material. Examples of cooling fire retardant materials are aluminum hydroxide and magnesium hydroxide. Another class of fire retardant material operates by release of gas that interferes with the flame. Examples of this class are the halogens, such as bromine and chlorine.
Another class of fire retardants use the mechanism known as “intumescence,” and is attributable to the fire retardant category known as “intumescents.” Intumescent fire retardants expand and form a char layer as a barrier between the underlying material and surrounding environment. This char layer is hard to burn, and insulates and protects the underlining material from burning. Intumescents operate by expansion either as a result of a chemical reaction under heat, or as by a primarily physical reaction that occurs due to the configuration of components in the intumescent material. Examples of chemical intumescents include phosphate-based materials and silica gel/potassium carbonate mixtures. Examples of physical intumescents include expandable graphite.
Flame retardants can be used with a wide variety of items such as furniture, floors (e.g., floor coverings), decks (e.g., deck coverings), textiles, cables, building materials and insulation, electrical equipment, transportation equipment (e.g., truck-bed liners), roofs (e.g., roof coating), and the like. Flame retardants are desirably used in two-part, isocyanate-base, curable systems to provide cured compositions with flame retardancy, but often such use is not a reality because of technical hurdles involved in incorporating flame retardants in two-part, curable systems.
Two-part, isocyanate-based, curable systems are well-known. Such systems generally include a compound having isocyanate functionality (NCO functionality) in a first part (or A-side) and a material reactive with the NCO functionality in a second part (or B-side). The first part and second part are typically stored in separate packages/containers until it is time to form the cured composition. At the time of use (i.e., time to form a cured composition) the first and second parts of such systems can be mixed together, applied to a surface or used in a desired manner, and allowed to cure (often at relatively low temperatures such as room temperature) to form a cured composition, such as a coating having useful properties such as a wide range of flexibility yet suitable toughness, high abrasion resistance, high chemical resistance, high acid etch resistance, high weatherability, and the like. Such coatings have found commercial success in vehicle products (e.g., truck bed liner), roof products (e.g., roof coating), and floor products (e.g., floor coating).
Materials that are reactive with isocyanate functionality to form such cured compositions include hydroxyl functional compounds to form polyurethanes, amine functional compounds to form polyureas, combinations of these, and the like.
Each part of the two-part curable system can desirably include additional ingredients that enhance the processing and/or handling of the parts (e.g., mixing the individual parts, mixing the parts together, applying the two-part mixture as a coating, and the like) and/or characteristics of the final cured composition. In general, it is desirable to incorporate the additional ingredients in one or both of the first and second parts so that fewer separate parts need to be handled prior to and at time of mixing the two parts. Optionally, additional components can be added as a third part at time of use (i.e., at the time of mixing the first and second part).
As mentioned, it is often desirable to include one or more flame retardants as additional ingredients in such two-part, isocyanate-based, curable systems. Certain desirable flame retardant ingredients, typically in solid form, for use in such curable systems are required to be present in relatively high amounts to be effective (e.g., greater than 25% by weight based on the total weight of the curable composition (e.g., first and second parts together)). Such flame retardant ingredients might have to be allocated among the first and second parts because loading such high levels of solids in only one part (e.g., 25% by weight of the total curable system is typically about 50% by weight of one part) tends to make that part hard to process and handle (e.g., the viscosity of that part is too high). Unfortunately, some flame retardant ingredients such as the phosphate-based, ammonium polyphosphate, and nitrogen-based, melamine are reactive with the NCO functionality in the first part of a two-part, isocyanate-based, curable system, and can result in undue reaction with the NCO functionality, e.g., prior to use such as during storage, and can compromise physical properties, rheological properties, curing properties, etc. While if used alone, such flame retardant ingredients tend not to be sufficiently effective.
Polyurethane, polyurethane/urea or polyurea polymer system systems have been provided in the form of coating compositions and solid body cast materials. See, e.g. U.S. Pat. No. 6,552,100.
There is a continuing need for new and improved flame retardant systems, especially those that can be used in two-part, isocyanate-based, curable systems to provide useful flame retardant properties in the cured composition.